1. Field of the Invention
The present invention relates to a data control apparatus for generating backup data of video and audio data having been edited and a recording medium that stores a program for generating backup data of video and audio data having been edited, and further relates to a data backup apparatus that is provided with the data control apparatus and records the generated backup data in a recording medium.
2. Related Art
Generally, one program is produced by extracting portions to be used from material data having a length several times longer than the data actually used as a main program. At this occasion, it is necessary to perform an operation of selecting only the needed portions from the large amount of video and audio material data and arranging the video data and the audio data in a desired order.
Conventionally, such an operation is achieved by linear editing with a video tape recorder (VTR). For example, only the needed portions of multiple material data are coupled on one video tape by repeating the following operations: copying a needed portion of a certain material data to a video tape; and copying a needed portion of another material data to a position of the video tape immediately subsequent thereto. In this way, the result of the editing (hereinafter referred to as “main program data”) is recorded onto one video tape through the linear editing.
Recently, along with the advancement of digital technologies, non-linear editing, in which video and audio are edited as digital data with a non-linear editing machine (for example, a computer), is coming into wide use to replace the linear editing conventionally performed. In the non-linear editing, generally, material data “a” and “b” as shown in FIGS. 8A and 8B are stored as data files FVa, FAa, FVb, FAb on a hard disk drive (HDD) of the non-linear editing machine. In the non-linear editing, the extraction of the portions to be used as the main program is performed by generating and rewriting editing information indicating the portions to be used as the main program. Due to the HDD's high performance in random access, it is not necessary to generate and save the main program data as shown in FIG. 8C on a tape and the like. Accordingly, in the case where the main program data is not generated, the main program data is reproduced by reading the needed portions Va, Aa, Vb, Ab of the material data “a” and “b” from the HDD in accordance with the editing information every time a need arises.
Because of the limitation on the recording capacity of the HDD, it may be necessary to replace the material data in the HDD when another program is produced. At this time, the material data “a” and “b” and the editing information currently stored in the HDD are moved as backup data as shown in FIG. 8D to an external recording medium such as a backup tape of a computer and the like by a data backup apparatus so that the currently produced program can be reproduced or re-edited later. A conventional data backup apparatus writes the data on the HDD onto an external recording medium in units of files (for example, see JP-A-2001-6274).
The conventional data backup apparatus sequentially writes the data in units of files, and therefore, as shown in FIG. 8D, the used portions Aa, Va, Ab, Vb of the material data stored in the external recording medium are physically placed at positions away from each other on the external recording medium due to the existence of unused portions Aa−, Aa+, Va−, Va+, Ab−, Ab+, Vb−, Vb+. Accordingly, even if the files, such as the audio file FAa, the video file FVa, the audio file FAb, the video file FVb, . . . , are sequentially read out in this order from the external recording medium, the video and audio cannot be synchronously reproduced in the same manner as a video tape for a VTR. Therefore, in order to reproduce the main program data using the backed-up material data, it is necessary to read the entire backed-up data written to the external recording medium to the HDD and generate and reproduce the main program data based on the editing information.
The more the amount of the material data stored in the external recording medium is, the more time it takes to read the backed-up data on the HDD. Therefore, there is a problem in that the operation of reproducing the main program data cannot be easily performed. Further, since the material data is stored in the external recording medium in units of files, it is necessary to load all of the material data including the unused portions into the HDD. Therefore, there is a problem in that when the HDD does not have a sufficiently large free space, the entire material data stored in the external recording medium cannot be read into the HDD, and the main program data cannot be reproduced. In this way, the conventional data backup apparatus has a problem in that, when the program using the backed-up material data is reproduced, a sufficiently large free space is necessary in the HDD of the non-linear editing machine, and it takes a great amount of time to read the data from the external recording medium. Therefore, the synchronous reproduction of the video and audio of the main program data cannot be easily performed.